Glass to metal seal in a coaxial cable



May 8, 1951 M. KUHNER GLASS TO METAL SEAL IN A COAXIAL CABLE Filed July l. 1947 FIG. 2

A T TOR/VEV Patented May 8, 1951 GLASS T METAL SEAL IN A COAXIAL CABLE Maxime Khner, Paris, France, Yassignmto International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application Ju1y,1, 1947, Serial Nc. 758 ,393 In France April 23,1945

Section 1,.Public Law 690, August 8, 1946 Patent expires April 23, 1965 2 Claims. (Cl. 174-22) also involves a novel combination of means suitable for carrying out the processes.

The present invention aims particularly at constructing a type Aof coaxial lead-in joint that limits the high frequency losses and Ythedampings. It accordingly provides for reducing to a minimum the insulating mass, which is assumed to be glass in order to make the explanation more understandable, and for selection of its location so as to place it in the most favorable field Zone.

It also provides a sealing process, e. g. of glass to metal, thatrnakes possible..,theconstruction of coaxial lead-in joints, particularly for collecting the vhigh frequency power available within electric discharge vessels and resonantcavities, or for forming coaxialicavities of :variable length for variable wave-length tubes, for example a tube of the type `disclosed plication No. 680,360^led-June-29, 1946, now abandoned.

The coaxial lead-inl joints that serve for collecting the power-generated within a resonant chamber that forms part of an electric discharge vessel, e. g.` a vacuum tube, vrequire the -use of a hermetic sealing.Y They consequently necessitate the presence in the-high frequency field of a glass mass that occasions losses and dampings.

In describing my invention I shall make reference to the accompanying drawings in which- Figs. 1 and la show in cross section coaxial conductors for very high frequency, wherein the sealing process has been performed according to the prior art,

Figs. 2 and 2a illustrate coaxial conductors and a heating element whereby my novel process is exemplified,

Fig. 3 illustrates a glass plate and axial system, and

Fig. i shows the structure of a coaxial lead-in joint assembly as fabricated by my novel process.

The customary methods of sealing, as shown the manner of sealing between the outer conductor of a coinAcopending U. Shapin Figs. 1 and la, make it difficult tov eliminate the above-mentioned drawbacks. Indeed, the glass mass 3 (Fig. l) is of considerable size and occupies, quite alittle space along the axis of the coaxiall inner conductor. Furthermore, in the eld of ultra-high frequencies, it is difficult to localize theY seal in a zone where the electric field is of zero intensity, or at most is very weak. An-

other drawback heretofore encountered, which' the present invention aims to overcome, has to do with the energy losses .due to wave reflections where the inner conductor element 4 must be reduced in diameter at the end Vin order to be screwed into another inner conductor element 2. According to one of its features, the invention provides for the use as the glass mass of a fiat disc of slight thickness which can be positioned inthe most favorable part of the electric field.

According to another feature of the invention,

the sealing of the central conductor of the coaxial system and the glass plate is effected on an expanded sleeve threaded on one of the elements of the Vcentral conductor and integraly with another element of the central conductor.

According to another feature of the invention, the walls of the sleeve are thin, not only for facilitating the sealing but also for insuring the continuity of the diameter of the central conductor of the coaxial system.

According to another feature of the invention, one of the elements of the outer conductor of the coaxial system is sealed to the glass plate, while at the same time providing by any suitable means the possibility of an electric connection between the sealed part and another element of the outer conductor.

According to another feature of the invention, the sealing is effected by any suitable welding means, and particularly. by high frequency heating accompanied by the use of known pressure means, or else, according to a preferred embodiment of the invention, by the weight itself of the parts to be welded to the glass plate.

In Fig. 2, a high frequency oven I is shown as a cylindrical holder for a wire heating coil. On a steatite mold 2 there is placed a glass plate 3 oriced in the middle by a circular hole having a diameter very slightly larger than that of the central conductor of the coaxial system. This central conductor consists of two separable elements 4 and 5 which may be screwed together or otherwise inter-connected. The electrical connection between the elements is effected by giving a slightly conical shape to element 5 so that it can be forced into sleeve 6, it being possible, if

necessary, to make this electric contact more perfeet by welding sleeve 6 to element 5 of the conductor. Sleeve B is given a somewhat expanded shape in order that its diameter may be slightly greater than that of the cylindrical hole provided in the glass plate 3.

Fig. 2a illustrates, with the same reference numbers, element 4 of the central conductor of the coaxial system once the sealing is done. In order to eiect the Welding, it is suiiicient to heat the assembly of the parts to be welded, e. g. by means of the high frequency oven l. The weight of the central conductive element 5 is usually sucient to eect the sealing between the glass plate 3 and the wall of sleeve 6. It will be understood, however, where the weight of the element 5 may be insufcient, pressure may be applied in any suitable manner in order to eiect the sealing together of the parts. Furthermore it will be observed that the glass plate may be located with suiiicient precision, disregarding its thickness, so that it will occupy the most favorable electric eld zone of the coaxial system. It is also evident, as a result of the formation of the central conductor and the means employed for obtaining electric continuity of the conductors two elements, that no partial reiiection of the transmitted wave will occur, and that the losses of high frequency power in the coaxial system will accordingly be reduced to a minimum.

Fig. 3 illustrates the manner of sealing the outer conductor of the coaxial system. The glass plate 3, to which element i of the central conductor has been sealed, is turned over and is laid on the steatite mold 2, as in the case of Fig. 2. Element 7 of the outer conductor, which has its end beveled or otherwise suitably shaped, is placed on the glass plate 3 within the high frequency oven l. The sealing is eiected in the manner already explained for the central conductor, the beveled portion 9 is pressed into the glass plate. A threaded portion il! of larger diameter than the plate 3 is left free to `be screwed into an internally threaded connecting member Il as shown in Fig. 4, whereby continuity of the outer conductor is obtained.

It is evident that the manner of sealing shown in Fig. 3, with the central conductor left out, is applicable to the assembling of any disc, of glass or any other material, with any metallic support, and particularly to the sealing of plates that are optically plane or have any other shape that it is desired to make with precision.

Fig. 4 illustrates, with the same reference numbers as in the preceding gures, the coaxial lead-in joint assembly after the conductors of the coaxial system are sealed to the glass plate 3. The glass plate 3 when welded at points 8 and 9, serves to complete the enclosure of an her- 4 metically sealed cavity I2, within the outer conductor 7. The high frequency power generated within the resonant cavity is transmitted to outside by means of element 5 of the central conductor and element ll or" the outer conductor of the coaxial system.

The eld of application of the present invention is not restricted to the particular embodiments explained above. These applications are given only by Way of example and without intending to limit the scope of the invention.

By those skilled in the art, the processes set forth above and the product itself may be varied considerably without departing from the spirit of my invention.

I claim:

1. Micro-wave transmission apparatus having coaxial conductors at least one section of which is to be hermetically sealed against the surrounding atmosphere, said apparatus having its inner conductor sections lnale-and-female threaded for joining together, the section which is female-threaded being provided with a thinwalled metal sleeve which extends beyond the threaded portion, a relatively thin annular disc of insulating material transversely across the space between said sleeve and said outer conductor, said outer conductor being sectioned and formed with male-and-female threaded ends for joining together, the root diameter of the male threads being greater than the diameter of said insulating disc, and the section end which is male-threaded having a beveled wall sealed in the `face of said disc close to the periphery thereof.

2. Apparatus according to claim 1 wherein said sleeve is substantially barrel-shaped and its outer wall provides continuity of wave-conducting surfaces with respect to an adjoining inner conductor section, which section is of reduced diameter at the end which is enclosed within said sleeve.

MAXIME KHNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED sTATEs PATENTS 

